Isolate DNA from a plant tissue (LC 2026) (Leaving Cert Biology): Revision Notes

Isolate DNA from a plant tissue

Materials needed:

• Kiwi
• Washing up liquid
• Table salt
• Protease enzyme
• Ice cold ethanol

Method:

1. Chop the kiwi into small pieces.
2. Add the chopped kiwi to a beaker containing a salt and washing-up liquid solution, then stir.

• Chopping the kiwi breaks down the cell wall, increasing surface area.
• The detergent dissolves the cell membranes
• The salt helps the DNA to clump together.

3. Place the beaker in a water bath at 60°C for exactly 15 minutes.

• This denatures the enzymes that would breakdown the DNA.

4. Cool the mixture by placing the beaker in an ice-water bath for 5 minutes.

• Stops breakdown of DNA.

5. Pour the mixture into a blender and blend for no more than 3 seconds.

• Further breaks down the cell wall, but blend for no more than 3 seconds to avoid DNA degradation.

6. Carefully philtre the mixture into a second beaker.
7. Transfer some of the filtrate into a boiling tube.
8. Add 2-3 drops of protease to the boiling tube.
9. Slowly trickle ice-cold alcohol down the side of the boiling tube.

• This separates DNA from the filtrate.
• DNA is insoluble in cold ethanol. The DNA will rise to the ethanol-filtrate boundary.

10. Observe any changes at the interface of the alcohol and the filtrate.
11. Using a glass rod, gently draw the DNA out from the alcohol layer.
12. Record the result.